Solvent free copper extraction
The system and method described herein provides a system and method for using ion-exchange resins to remove excess copper during processes such as PCB (Printed Circuit Board) fabrication using cupric chloride etchants. Cu +2 is used to oxidize solid copper producing two Cu + ions. During operation, the etchant is overloaded with copper ions and an extraction system is implemented to control the concentration and remove excess copper. Traditional systems use liquid extractions but these systems can be costly and use hazardous solvents. Ion-exchange resins serve as a solution for controlling the concentration, absorbing metal ions and retaining them until desorption. The system and method further determines the effectiveness of the resin in removing the copper based on performing adsorption and desorption at varying flow rates. The results showed that the resin effectively removes copper at various flowrates, removing an average of 10.06 g/l Cu from a bulk value of three beds of etchant.
1 . A method comprising:
causing etchant to flow through a resin column comprising resin, the resin column removing less than an entire amount of copper from the etchant to create regenerated etchant, wherein the amount of copper removed from the etchant is a function of:
a volume of the etchant treated,
a size of the resin column, and
an initial mass flow rate of the etchant through the resin column;
desorbing, using sulfuric acid electrolyte, an amount of copper from the resin;
determining an inlet mass flow rate of the copper based on a value corresponding to a volumetric flow rate, volume of the resin, and feed copper concentration;
determining, based on at least the amount of copper from the resin and the inlet mass flow rate, an effectiveness of the resin column in removing the amount of copper from the etchant; and
applying the regenerated etchant to one or more subsequent etching processes.
2 . The method of claim 1 , wherein the resin comprises an ion-exchange resin, wherein the resin column adsorbs copper ions from the etchant using the ion-exchange resin and releases protons into the etchant to maintain a charge balance.
3 . The method of claim 2 , wherein a type of the resin is chosen based at least on one factor related to a pH value associated with adsorption of copper ions.
4 . The method of claim 3 , wherein the removing of the copper and the releasing of the protons increases the pH value of the etchant.
5 . The method of claim 3 , wherein a specific gravity of the etchant drops in response to the removal of the copper.
6 . The method of claim 1 , wherein desorbing the extracted copper comprises:
removing copper ions from the resin, wherein protons remain in the resin.
7 . The method of claim 1 , wherein a flow of etchant through the resin column is caused by a pump.
8 . The method of claim 7 , further comprising:
treating the resin column by air purging, rinsing with water, followed with air purging.
9 . The method of claim 1 , wherein a temperature of the etchant changes during adsorption.
10 . The method of claim 1 , wherein the amount of copper removed from the etchant is based on volumetric flow rates through the resin and feed copper concentrations.
11 . The method of claim 1 , wherein time required to desorb the extracted copper from the resin is based on a function of the volumetric flow rate of the sulfuric acid electrolyte.
12 . The method of claim 1 , wherein the etchant comprises at least cupric copper.
13 . The method of claim 1 , wherein the amount of copper that is removed is calculated from the formula:
M
.
=
[
Feed
Concentration
[
g
l
]
*
Volumetric
Flow
Rate
[
l
Hr
]
1000
[
g
kg
]
*
Resin
Volume
[
l
]
]